ES-O3-M

portable, handheld dissolved ozone meter

overview

Direct measurements of dissolved O3 for waste water monitoring and scientific research

Extremely stable signal for accurate and reliable measurements

Portable meter or online, continuous monitoring options

The microprocessor-operated measuring instrument has been developed for the fast and accurate in-situ determination of dissolved ozone without any sampling.

The instrument is useful for the laboratory and for simple and fast measurements in the field (e.g. swimming pools, drinking water, chemical industry). The instrument is equipped with an amperometric, membrane covered O3-micro-sensor, which has not to be streamed and with a temperature-sensor. The display shows the concentration of the measured dissolved ozone in mg/l and the temperature of the sample.

The measuring instrument is powered via the included power supply unit and can be operated also with batteries. The RS 232 interface allows to link the instrument to a PC or notebook.

By exchanging the O3-sensor tip against a galvanic oxygen micro-sensor tip, the measuring instrument could be changed fast and simply into a high performance oxygen measuring instrument. Furthermore the instrument is useful to store the calibration coefficients of up to 10 different chemical micro-sensors and to calculate the concentration units by means of the measured raw data. This allows also the fast and simple exchange of sensors and measuring ranges, if required.

the ES-O3-M advantage

Compared with the other commercially available so called macro-sensors and compared with the other available high-tech and very expensive instruments (especially optical instruments), the new measuring instrument with amperometric micro-sensor has the following advantages:

1. No streaming of the sensor’s membrane necessary, very low analyte consumption
2. No exchange of membrane or electrolyte for maintenance
3. Very fast response time of the sensor (some seconds for t90%)
4. Analysis without any sampling or adding of chemicals
5. Very low detection limit: down to 0,02 mg/l
6. High accuracy
7. High economic efficiency (no chemical consumption)
8. Measurements also possible in turbid, coloured, muddy and salt containing samples
9. Continuous on-line measurements (not only average measurements of a big volume)
10. High local resolution of the measurements (μm-steps)
11. Immediate display of the ozone concentration (mg/l)

the working principle of the O3 sensor

Because of the partial pressure of gaseous ozone dissolved in the sample, the analyte is separated by permeation through the membrane. The membrane is only pervious for gases, so that liquids, ions and solids are not able to reach the inner electrolyte of the sensor.

The sensor contains inside an electrolyte with a redox catalyst (= redox mediator) and 3 electrodes. The electrode materials have been choosen and prepared very carefully to realize ideal electrochemical conditions.

At the electrodes a special polarization voltage is adjusted to realize a well-defined concentration ratio of the oxidized and of the reduced form of the redox catalyst. The time for the polarization, realized by means of the sensors integrated electronic device is approximately 5-10 minutes. If the ozone now passes the membrane, it reacts first chemically with the redox catalyst to form a reaction product followed by the electrochemically reduction of the reaction product at the working electrode. Caused by the polarization voltage the system is now endeavoured to adjust the former concentration ratio. This causes a current similar to the dissolved ozone amount of the sample. Besides, the current flow in the amperometric sensor leads to a rapid decrease of the analyte inside the sensor resulting in very fast response times also, if a rapid change from high to very low concentration levels is necessary.

All electrochemically working sensors have to be combined with a temperature measurement and the amperometric ozone sensor too. When ordering a multisensor measuring system for laboratory use or a complete submersible probe system, the temperature measurement and the temperature correction of the sensor signal is already included.

If measurements in a flow through system are required, special temperature sensors for the integration in AMT flow through cells are offered. When measuring in opened vessels or beakers in the laboratory, the customers has to realize the temperature measurement themselves.

If a calibrated sensor is ordered, the temperature correction is very easy by means of a factor or for more accurate measurements by means of a mathematical formula, delivered with the sensor.